Electrode composite body, method of manufacturing electrode composite body, and lithium battery

ABSTRACT

An electrode composite body includes: an active material molded body including active material particles which include a lithium composite oxide and have a particle shape, and a communication hole that is provided between the active material particles; a first solid electrolyte layer that is provided on a surface of the active material molded body, and includes a first inorganic solid electrolyte; and a second solid electrolyte layer that is provided on the surface of the active material molded body, and includes a second inorganic solid electrolyte of which a composition is different from a composition of the first inorganic solid electrolyte, and which contains boron as a constituent element and is crystalline.

This application claims a priority to Japanese Patent Application No.2015-115507 filed on Jun. 8, 2015 which is hereby expressly incorporatedby reference in its entirety.

BACKGROUND

1. Technical Field

Several aspects of the present invention relate to an electrodecomposite body, a method of manufacturing the electrode composite body,and a lithium battery.

2. Background Art

As a power supply of various electrical apparatuses including a portableinformation apparatus, a battery such as a lithium battery (including aprimary battery and a secondary battery) has been used. The lithiumbattery includes a positive electrode, a negative electrode, and anelectrolyte layer that is provided between layers of the positiveelectrode and the negative electrode and mediates lithium ion conductiontherebetween.

Recently, as a lithium battery in which a high energy density andstability are compatible with each other, there is suggested anall-solid type lithium battery that uses a solid electrolyte in aformation material of the electrolyte layer (for example, refer toJP-A-2006-277997, JP-A-2004-179158, and Japanese Patent No. 4615339).

Additional high output and high capacity are demanded for the all-solidtype lithium battery, but it cannot be said that these characteristicsare sufficiently obtained in the all-solid type lithium battery of therelated art.

SUMMARY

An advantage of some aspects of the invention is to provide an electrodecomposite body capable of realizing a lithium secondary batteryexhibiting a stable charge and discharge cycle when being applied to thelithium secondary battery, a method of manufacturing an electrodecomposite body which is capable of manufacturing the electrode compositebody, and a lithium battery that includes the electrode composite bodyand exhibits the stable charge and discharge cycle.

The advantage can be accomplished by the following aspects of theinvention.

An electrode composite body according to an aspect of the inventionincludes: an active material molded body including active materialparticles which include a lithium composite oxide and have a particleshape, and a communication hole that is provided between the activematerial particles; a first solid electrolyte layer that is provided ona surface of the active material molded body, and includes a firstinorganic solid electrolyte; and a second solid electrolyte layer thatis provided on the surface of the active material molded body, andincludes a second inorganic solid electrolyte of which a composition isdifferent from a composition of the first inorganic solid electrolyte,and which contains boron as a constituent element and is crystalline.

According to this configuration, an electrode composite body, which iscapable of realizing a lithium secondary battery exhibiting a stablecharge and discharge cycle when being applied to the lithium secondarybattery, is obtained. In addition, since the second inorganic solidelectrolyte is crystalline, material-intrinsic charge mobility issufficiently exhibited. Accordingly, it is possible to sufficientlycompensate a reduction in charge migration, which is caused bydeficiency of the first solid electrolyte layer in the communicationhole of the active material molded body, by the secondary solidelectrolyte layer. As a result, it is possible to attain high capacityand high output of a lithium secondary battery.

In the electrode composite body according to the aspect of theinvention, it is preferable that the lithium composite oxide is LiCoO₂.

According to this configuration, the active material particles allowcharge migration between the active material particles and the secondinorganic solid electrolyte to be more smoothly performed. According tothis, a lithium secondary battery including the lithium composite oxidecan realize a more stable charge and discharge cycle.

In the electrode composite body according to the aspect of theinvention, it is preferable that the first inorganic solid electrolyteis Li_(7-x)La₃(Zr_(2-x), M_(x))O₁₂.

In the formula, M represents at least one kind of element selected fromNb, Sc, Ti, V, Y, Hf, Ta, Al, Si, Ga, Ge, Sn, and Sb, and X represents areal number of 0 to 2].

According to this configuration, a first inorganic solid electrolyte, inwhich an unintended reaction with the second inorganic solid electrolyteis hardly caused to occur, is obtained. In addition, when using thefirst inorganic solid electrolyte as described above, it is possible tofurther raise the charge mobility between the active material moldedbody and the first solid electrolyte layer.

In the electrode composite body according to the aspect of theinvention, it is preferable that the second inorganic solid electrolyteis Li_(2+X)B_(X)C_(1-X)O₃ (X represents a real number that is greaterthan 0 and less than 1).

According to this configuration, a second inorganic solid electrolyte,which is less likely to be affected by moisture and has relatively highcharge mobility, is obtained. In addition, when using the secondinorganic solid electrolyte as described above, ion conductivity in theelectrode composite body is enhanced. As a result, an electrodecomposite body, which is capable of realizing a lithium secondarybattery in which reliability is high over a long period of time and highcapacity and high output are attained, is obtained.

A method of manufacturing an electrode composite body according toanother aspect of the invention includes: supplying a solution of afirst inorganic solid electrolyte to come into contact with an activematerial molded body including active material particles which include alithium composite oxide and have a particle shape, and a communicationhole that is provided between the active material particles so as toimpregnate the solution into the communication hole; heating the activematerial molded body that is impregnated with the solution; supplying asolid material of a second inorganic solid electrolyte, of which acomposition is different from a composition of the first inorganic solidelectrolyte and contains boron as a constituent element, to come intocontact with the active material molded body; melting the solid materialof the second inorganic solid electrolyte, and impregnating theresultant molten material of the second inorganic solid electrolyte intothe communication hole; and solidifying the molten material to becrystallized.

According to this configuration, it is possible to efficientlymanufacture an electrode composite body capable of realizing the lithiumsecondary battery that exhibits the stable charge and discharge cycle.

A method of manufacturing an electrode composite body according to stillanother aspect of the invention includes: supplying a solid material ofa first inorganic solid electrolyte and a solid material of a secondinorganic solid electrolyte, of which a melting point is lower than amelting point of the first inorganic solid electrolyte and whichcontains boron as a constituent element, to come into contact with anactive material molded body including active material particles whichinclude a lithium composite oxide and have a particle shape, and acommunication hole that is provided between the active materialparticles; melting the solid material of the second inorganic solidelectrolyte, and impregnating the resultant molten material of thesecond inorganic solid electrolyte into the communication hole incombination with the solid material of the first inorganic solidelectrolyte; and solidifying the molten material to be crystallized.

According to this configuration, it is possible to efficientlymanufacture an electrode composite body capable of realizing the lithiumsecondary battery that exhibits the stable charge and discharge cycle.

A lithium battery according to yet another aspect of the inventionincludes: the electrode composite body according to the aspect of theinvention; a current collector that is provided on one surface of theelectrode composite body to come into contact with the active materialmolded body; and an electrode that is provided on the other surface ofthe electrode composite body to come into contact with the first solidelectrolyte layer or the second solid electrolyte layer.

According to this configuration, a lithium secondary battery, whichexhibits the stable charge and discharge cycle, is obtained. Inaddition, a lithium secondary battery, in which high capacity and highoutput are attained, is obtained.

It is preferable that the lithium battery further includes a third solidelectrolyte layer that is provided between the electrode composite bodyand the electrode, and includes a third inorganic solid electrolyte thatcontains boron as a constituent element and is amorphous.

According to this configuration, a lithium secondary battery, whichexhibits the stable charge and discharge cycle over a longer period oftime, is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a longitudinal cross-sectional view illustrating a lithiumsecondary battery to which a first embodiment of a lithium batteryaccording to the invention is applied.

FIGS. 2A and 2B are views illustrating a method of manufacturing thelithium secondary battery illustrated in FIG. 1.

FIGS. 3A and 3B are views illustrating a method of manufacturing thelithium secondary battery illustrated in FIG. 1.

FIGS. 4A and 4B are views illustrating a method of manufacturing thelithium secondary battery illustrated in FIG. 1.

FIGS. 5A and 5B are views illustrating a method of manufacturing thelithium secondary battery illustrated in FIG. 1.

FIGS. 6A and 6B are views illustrating a method of manufacturing thelithium secondary battery illustrated in FIG. 1.

FIGS. 7A and 7B are views illustrating a method of manufacturing thelithium secondary battery illustrated in FIG. 1.

FIGS. 8A and 8B are views illustrating a method of manufacturing thelithium secondary battery illustrated in FIG. 1.

FIG. 9 is a longitudinal cross-sectional view illustrating a secondembodiment of a lithium secondary battery that is manufactured byapplying the method of manufacturing a lithium battery according to theinvention.

FIG. 10 is a longitudinal cross-sectional view illustrating a thirdembodiment of a lithium secondary battery that is manufactured byapplying the method of manufacturing a lithium battery according to theinvention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an electrode composite body, a method of manufacturing theelectrode composite body, and a lithium battery according to theinvention will be described with reference to the accompanying drawings.

In addition, in the drawings which are used for the description,dimensions, ratios, and the like of respective constituent elements areappropriately made different for easy understanding of the drawings andfor easy understanding of explanation, but the difference in thedrawings is made for convenience. In addition, for convenience ofexplanation, an upper side and a lower side of the illustration will bedescribed as “upper” and “lower”, respectively.

First Embodiment

In this embodiment, description will be given of an electrode compositebody, a method of manufacturing the electrode composite body, and alithium battery according to the invention.

First, a lithium secondary battery 100, to which the lithium batteryaccording to the invention is applied, will be described. FIG. 1 is alongitudinal cross-sectional view of the lithium secondary battery 100.

The lithium secondary battery 100 includes a stacked body 10, and anelectrode 20 that is joined to the stacked body 10. The lithiumsecondary battery 100 is a so-called all-solid type lithium (ion)secondary battery.

The stacked body 10 includes a current collector 1, an active materialmolded body 2, a first solid electrolyte layer 3, and a second solidelectrolyte layer 5. In addition, in the following description, aconfiguration provided with the active material molded body 2, the firstsolid electrolyte layer 3, and the second solid electrolyte layer 5 isreferred to as an electrode composite body 4. The electrode compositebody 4 is located between a current collector 1 and the electrode 20,and a pair of opposite surfaces 4 a and 4 b are joined to the currentcollector 1 and the electrode 20, respectively. Accordingly, the stackedbody 10 has a configuration in which the current collector 1 and theelectrode composite body 4 are stacked.

The current collector 1 is an electrode that extracts a currentgenerated through a battery reaction, and is provided on one surface 4 aof the electrode composite body 4 to come into contact with the activematerial molded body 2 that is exposed from the first solid electrolytelayer 3 and the second solid electrolyte layer 5.

The current collector 1 functions as a positive electrode in a casewhere the active material molded body 2 is constituted by a positiveelectrode active material, and functions as a negative electrode in acase where the active material molded body 2 is constituted by anegative electrode active material.

In addition, examples of a formation material (constituent material) ofthe current collector 1 include one kind of metal (elementary metalsubstance) that is selected from the group consisting of copper (Cu),magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc(Zn), aluminum (Al), germanium (Ge), indium (In), gold (Au), platinum(Pt), silver (Ag), and palladium (Pd), an alloy including two or morekinds of metal elements selected from the group, and the like.

The shape of the current collector 1 is not particularly limited, andexamples thereof include a sheet shape, a foil shape, a network shape,and the like. In addition, a joining surface of the current collector 1with the electrode composite body 4 may be flat, or unevenness may beformed on the joining surface. In this case, it is preferable that thejoining surface is formed so that a contact area with the electrodecomposite body 4 becomes the maximum.

The active material molded body 2 is a porous molded body which includesparticle-like active material particles 21 that contains an activematerial as a formation material, and which is formed in such a mannerthat a plurality of the active material particles 21 arethree-dimensionally connected.

The active material molded body 2, which is the porous molded body, hasa plurality of pores. A vacancy in the plurality of pores is a void ofthe active material molded body 2. Portions, which communicate with eachother in a network shape at the inside of the active material moldedbody 2, form a communication hole. When the first solid electrolytelayer 3 enters the communication hole, it is possible to secure a widecontact area between the active material molded body 2 and the firstsolid electrolyte layer 3. In addition, the second solid electrolytelayer 5 is provided to bury a void that is not buried by the first solidelectrolyte layer 3. According to this, a gap between the activematerial particles 21 and granular bodies 31 is buried with the secondsolid electrolyte layer 5, and the second solid electrolyte layer 5contributes to enhancement of charge mobility between the activematerial particles 21 and the granular bodies 31. As a result, in thelithium secondary battery 100, stabilization of a charge and dischargecycle is attained.

The current collector 1 may function as a positive electrode or anegative electrode by appropriately selecting a kind of an activematerial formation material of the active material particles 21.

In a case where the current collector 1 is set as a positive electrode,as a formation material of the active material particles 21, forexample, a known lithium composite oxide may be preferably used as apositive electrode active material.

In addition, in this specification, the “lithium composite oxide”represents an oxide which essentially includes lithium, and includes twoor more kinds of metal ions as a whole, and in which existence of oxoacid ions is not recognized.

Examples of the lithium composite oxide include LiCoO₂, LiNiO₂, LiMn₂O₄,Li₂Mn₂O₃, LiFePO₄, Li₂FeP₂O₇, LiMnPO₄, LiFeBO₃, Li₃V₂(PO₄)₃, Li₂CUO₂,LiFeF₃, Li₂FeSiO₄, Li₂MnSiO₄, and the like. In addition, in thisspecification, a solid-solution, in which a part of atoms in a crystalof the lithium composite oxide is substituted with other transitionmetals, typical metals, alkali metals, alkali rare-earth elements,lanthanoids, chalcogenides, halogens, and the like, is included in thelithium composite oxide, and this solid-solution can also be used as thepositive electrode active material.

Among these, LiCoO₂ is preferably used as the lithium composite oxide.This active material allows charge migration to be more smoothlyperformed between the active material and a second inorganic solidelectrolyte that contains boron as a constituent element and iscrystalline. According to this, the lithium secondary battery 100, whichincludes the active material, can realize a more stable charge anddischarge cycle.

On the other hand, in a case where the current collector 1 is set as anegative electrode, with regard to the formation material of the activematerial molded body 2, for example, a lithium composite oxide such asLi₄Ti₅O₁₂ and Li₂Ti₃O₇ can be used as a negative electrode activematerial.

When including the lithium composite oxide, delivery of electrons isperformed between the plurality of active material particles 21, anddelivery of lithium ions is performed between the active materialparticles 21 and the first solid electrolyte layer 3, and thus theactive material particles 21 exhibit a function as the active materialmolded body 2 in a satisfactory manner.

An average particle size of the active material particles 21 ispreferably 300 nm to 5 μm, more preferably 450 nm to 3 μm, and stillmore preferably 500 nm to 1 μm. When using the active material havingthe average particle size, it is possible to set a porosity of theactive material molded body 2, which is obtained, in a preferable range.According to this, it is easy to increase a surface area of the activematerial molded body 2 on an inner side of the pores, and it is easy toincrease a contact area between the active material molded body 2 andthe first solid electrolyte layer 3. Accordingly, it is easy to allowthe lithium battery using the stacked body 10 to have high capacity.

Here, for example, the porosity can be measured from (1) the volume(apparent volume) of the active material molded body 2 including thepores which is obtained from external dimensions of the active materialmolded body 2, (2) the mass of the active material molded body 2, and(3) the density of an active material that constitutes the activematerial molded body 2 on the basis of the following expression (I).

Porosity (%)=[1−mass of active material molded body/((apparentvolume)×(density of active material))]×100   (I)

It is preferable the porosity is 10% to 50%, and more preferably 30% to50%. When the active material molded body 2 has the porosity describedabove, it is easy to increase a surface area of the active materialmolded body 2 on an inner side of the pores, and it is easy to increasea contact area between the active material molded body 2 and the firstsolid electrolyte layer 3. Accordingly, it is easy to allow the lithiumbattery using the stacked body 10 to have high capacity.

When an average particle size of the active material particles 21 isless than the above-described lower limit, a radius of the pores in theactive material molded body that is formed is likely to be as small asseveral nm in accordance with the kind of the formation material of thefirst solid electrolyte layer 3, and thus it is difficult to impregnatea liquid material including a precursor of the first inorganic solidelectrolyte into the pores. As a result, there is a concern that it isdifficult to form the first solid electrolyte layer 3 that comes intocontact with a surface on an inner side of the pores.

In addition, when the average particle size of the active materialparticles 21 is greater than the above-described upper limit, a specificsurface area that is a surface area per unit mass of the active materialmolded body 2 that is formed decreases, and thus there is a concern thatthe contact area between the active material molded body 2 and the firstsolid electrolyte layer 3 may decrease. According to this, there is aconcern that a sufficient output may not be obtained in the lithiumsecondary battery 100. In addition, an ion diffusion distance from theinside of the active material particles 21 to the first solidelectrolyte layer 3 is lengthened, and thus there is a concern that itis difficult for the lithium composite oxide in the vicinity of thecenter of the active material particles 21 to contribute to the functionof the battery.

In addition, for example, the average particle size of the activematerial particles 21 can be measured by obtaining a median diameter byusing a light-scattering type particle size distribution measuringdevice (nano track UPA-EX250, manufactured by Nikkiso Co., Ltd.) afterdispersing the active material particles 21 in n-octanol to have aconcentration in a range of 0.1% by mass to 10% by mass.

In addition, although details will be described later, the porosity ofthe active material molded body 2 can be controlled by using a poreforming material, which is composed of a particle-like organic material,in a process of forming the active material molded body 2.

A first inorganic solid electrolyte is set as a formation material(constituent material) of the first solid electrolyte layer 3, and thefirst solid electrolyte layer 3 is provided to come into contact withthe surface, which includes a surface of the active material molded body2 on an inner side of the pores (voids), of the active material moldedbody 2.

Examples of the first inorganic solid electrolyte include oxides,sulfides, halides, and nitrides such as SiO₂—P₂O₅—Li₂O, SiO₂—P₂O₅—LiCl,Li₂O—LiCl—B₂O₃, Li_(3.4)V_(0.6)Si_(0.4)O₄, Li₁₄ZnGe₄O₁₆,Li_(3.6)V_(0.4)Ge_(0.6)O₄, Li_(1.3)Ti_(1.7)Al_(0.3) (PO₄)₃,Li_(2.88)PO_(3.73)N_(0.14), LiNbO₃, Li_(0.35)La_(0.55)TiO₃,Li₇La₃Zr₂O₁₂, Li₂S—SiS₂, Li₂S—SiS₂—LiI, Li₂S—SiS₂—P₂S₅, LiPON, Li₃N,LiI, LiI—CaI₂, LiI—CaO, LiAlCl₄, LiAlF₄, LiI—Al₂O₃, LiF—Al₂O₃,LiBr—Al₂O₃, Li₂O—TiO₂, La₂O₃—Li₂O—TiO₂, Li₃NI₂, Li₃N—LiI—LiOH,Li₃N—LiCl, Li₆NBr₃, LiSO₄, Li₄SiO₄, Li₃PO₄—Li₄SiO₄, Li₄GeO₄—Li₃VO₄,Li₄SiO₄—Li₃VO₄, Li₄GeO₄—Zn₂GeO₂, Li₄SiO₄—LiMoO₄, and LiSiO₄—Li₄ZrO₄. Inaddition, the first inorganic solid electrolyte may be crystalline oramorphous. In addition, in this specification, a solid-solution, inwhich a part of atoms of the compositions is substituted with othertransition metals, typical metals, alkali metals, alkali rare-earthelements, lanthanoids, chalcogenides, halogens, and the like, can beused as the first inorganic solid electrolyte.

In addition, among the above-described materials, as the first inorganicsolid electrolyte, particularly, an electrolyte that does not containboron as a constituent element is preferably used, and a lithiumcomposite oxide that contains La and Zr as the constituent element ismore preferably used.

Specifically, a lithium composite oxide expressed by the followingFormula (II) can be exemplified.

Li_(7-x)La₃(Zr_(2-x),M_(x))O₁₂  (II)

In Formula, M represents at least one kind of element selected from Nb,Sc, Ti, V, Y, Hf, Ta, Al, Si, Ga, Ge, Sn, and Sb, and X represents areal number of 0 to 2.

In addition, particularly, in Formula (II), it is preferable that M isat least one kind of element among niobium (Nb) and tantalum (Ta).According to this, it is possible to further raise lithium ionconductivity of the first inorganic solid electrolyte that is obtained,and it is possible to further enhance the mechanical strength of thefirst inorganic solid electrolyte.

In addition, in Formula (II), X, that is, a substitution rate of themetal M is preferably 1 to 2, and more preferably 1.4 to 2. When X istoo small, there is a concern that the above-described function may notbe sufficiently exhibited in the first inorganic solid electrolyte inaccordance with the kind of the metal M.

In addition, the lithium composite oxide illustrated in Formula (II) mayhave any crystal structure such as cubic and tetragonal, but it ispreferable that the lithium composite oxide has a cubic garnet typecrystal structure. According to this, an additional improvement in theion conductivity of the first inorganic solid electrolyte is attained.

In addition, more specifically, Li_(6.8)La₃Zr_(1.8)Nb_(0.2)O₁₂ is morepreferably used.

When the first inorganic solid electrolyte as described above exists incombination with a second inorganic solid electrolyte containing boronas a constituent element, an unintended reaction with the secondinorganic solid electrolyte is hardly caused to occur. Accordingly, whenusing the first inorganic solid electrolyte as described above, it ispossible to further raise the charge mobility between the activematerial molded body 2 and the first solid electrolyte layer 3.

The first inorganic solid electrolyte, which is a constituent materialof the first solid electrolyte layer 3, is generated by baking (heating)a precursor of the first inorganic solid electrolyte. During the baking,the first inorganic solid electrolyte that is generated constitutes thegranular bodies 31 each of which is composed of a secondary particlethat is formed through granulation of primary particles. According tothis, the first solid electrolyte layer 3 is provided to come intocontact with the surface, which includes a surface of the activematerial molded body 2 on an inner side of the pores, of the activematerial molded body 2. When considering that the first solidelectrolyte layer 3 is configured as an aggregate of the granular bodies31, as is the case with the active material molded body 2, the firstsolid electrolyte layer 3 is also configured as a porous body.

It is preferable that the ion conductivity of the first solidelectrolyte layer 3 is 5×10⁻⁵ S/cm or greater, and more preferably1×10⁻⁵ S/cm or greater. When the first solid electrolyte layer 3 has theion conductivity, ions, which are included in the first solidelectrolyte layer 3 at a position distant from the surface of the activematerial molded body 2, also reach the surface of the active materialmolded body 2, and can contribute to a battery reaction in the activematerial molded body 2. According to this, a utilization rate of theactive material in the active material molded body 2 is improved, andthus it is possible to increase the capacity. At this time, when the ionconductivity is less than the lower limit, in the active material moldedbody 2, only an active material in the vicinity of a surface layer on asurface side that faces a counter electrode contributes to the batteryreaction depending on the kind of the first solid electrolyte layer 3,and thus there is a concern that the capacity decreases.

In addition, the “ion conductivity of the first solid electrolyte layer3” represents “total ion conductivity” that is the sum of “bulkconductivity” of the above-described inorganic solid electrolyte thatconstitutes the first solid electrolyte layer 3, and “grain boundary ionconductivity” that is conductivity between crystal particles in a casewhere the inorganic solid electrolyte is crystalline.

In addition, for example, the ion conductivity of the first solidelectrolyte layer 3 can be measured as follows. First, solid electrolytepowders are press-molded into a tablet shape at 624 MPa, and theresultant press-molded body is sintered in an atmospheric atmosphere at700° C. for 8 hours. Then, a platinum electrode having a diameter of 0.5cm and a thickness of 100 nm is formed on both surfaces of thepress-molded body through sputtering, and the press-molded body is setas an object to be inspected. Then, the ion conductivity is measured byan AC impedance method. As a measurement device, for example, animpedance analyzer (manufactured by Solartron, model number: SI1260) isused.

A second inorganic solid electrolyte is set as a formation material(constituent material) of the second solid electrolyte layer 5, and asis the case with the first solid electrolyte layer 3, the second solidelectrolyte layer 5 is provided to come into contact with the surface,which includes a surface of the active material molded body 2 on aninner side of the pores (voids), of the active material molded body 2.

The second inorganic solid electrolyte is a solid electrolyte that iscapable of conducting lithium ions. In addition, the second inorganicsolid electrolyte has a composition different from that of the firstinorganic solid electrolyte, and is an inorganic solid electrolyte(hereinafter, also referred to simply as “boron-containing electrolyte”)that contains boron as a constituent element. The above-described secondinorganic solid electrolyte is less likely to be affected by moisture incomparison to a SiO-based electrolyte, and thus it is possible tofurther enhance long-term stability of the second solid electrolytelayer 5. That is, when penetration of moisture occurs, in the firstsolid electrolyte layer 3, a defect occurs in a conduction path oflithium ions, and thus conductivity decreases. However, when the secondsolid electrolyte layer 5 is formed, generation of the defect issuppressed. As a result, stabilization of the charge and discharge cycleis attained, and thus the lithium secondary battery 100, which isobtained, has higher reliability.

As described above, examples of the second inorganic solid electrolyteinclude a boron-containing electrolyte. Specifically, a lithiumcomposite oxide such as Li_(2+X)B_(X)C_(1-X)O₃ (X represents a realnumber of greater than 0 and less than 1) that contains boron as aconstituent element is used, and Li_(2.2)C_(0.8)B_(0.2)O₃ is preferablyused. Particularly, in a case of being crystalline, the second inorganicsolid electrolyte is less likely to be affected by moisture, and hasrelatively high charge mobility. According to this, when using thesecond inorganic solid electrolyte as described above, ion conductivityin the electrode composite body 4 is enhanced. As a result, in thelithium secondary battery 100 that is obtained, reliability is high overa long period of time, and additional stabilization in the charge anddischarge cycle is attained.

In addition, the second inorganic solid electrolyte is a crystallinesolid electrolyte. In the second solid electrolyte layer 5 including thesecond inorganic solid electrolyte, since the second inorganic solidelectrolyte is crystalline, material-intrinsic charge mobility issufficiently exhibited. According to this, it is possible tosufficiently compensate a reduction in charge migration, which is causedby deficiency of the first solid electrolyte layer 3 in the voids of theactive material molded body 2, by the second solid electrolyte layer 5.As a result, it is possible to attain high capacity and high output ofthe lithium secondary battery 100.

In addition, from the above-described viewpoint, a composition, which iscapable of being crystallized when being molted and solidified, isselected for the second inorganic solid electrolyte.

In addition, the “crystalline” in this specification includes both asingle crystal and a polycrystal.

In addition, for example, it is possible to specify whether or not thesecond inorganic solid electrolyte is crystalline in accordance withwhether or not a peak derived from a crystal is recognized in crystalstructure analysis by using X-ray diffraction (XRD).

In addition, for example, the second solid electrolyte layer 5 mayfurther include other solid electrolytes, for example, an inorganicsolid electrolyte (hereinafter, also referred to simply as“silicon-containing electrolyte), which contains silicon as aconstituent element, as necessary. Specifically, a lithium compositeoxide, which contains silicon as a constituent element, may beexemplified, and one or both of Li₂SiO₃ and Li₆SiO₅ are preferably used.

In this case, in the second solid electrolyte layer 5, thesilicon-containing electrolyte is included in a content rate less thanthat of the boron-containing electrolyte. According to this, the effect,which is exhibited by the above-described boron-containing electrolyte,can be necessarily and sufficiently exhibited.

An average grain size of a crystal included in the second solidelectrolyte layer 5 that is formed also varies depending on the size ofthe pores of the active material molded body 2, and thus there is noparticular limitation to the average grain size. However, it ispreferable that the average grain size is 5 μm to 200 μm, and preferably10 μm to 100 μm. When the average grain size of the crystal is set inthe above-described range, in the second solid electrolyte layer 5, thesecond inorganic solid electrolyte exhibits material-intrinsic chargemobility. According to this, when the inside of the pores of the activematerial molded body 2 is buried with the second solid electrolyte layer5, it is possible to attain high capacity and high output of the lithiumsecondary battery 100 in a more reliable manner.

In addition, for example, the average grain size of the crystal can beobtained by observing a cross-section of the electrode composite body 4with an electron microscope and the like, and by obtaining the maximumlength on the cross-section of the crystal of the second inorganic solidelectrolyte as a grain size, and by averaging 10 or more grain sizes.

In addition, although determined in accordance with the volume of thepores, as an example, the amount of the second solid electrolyte layer5, which is impregnated, is preferably 20% by volume or greater on thebasis of the volume of the first solid electrolyte layer 3, and morepreferably 30% by volume or greater. When a ratio between the volume ofthe second solid electrolyte layer 5 and the volume of the first solidelectrolyte layer 3 is set in the above-described range, balance betweenan operation driven by the first solid electrolyte layer 3, and aneffect driven by the second solid electrolyte layer 5 becomes optimized.As a result, it is possible to attain additional high capacity and highoutput of the lithium secondary battery 100 while attaining additionalstability of the charge and discharge cycle.

In addition, an organic material such as a binder for joining of activematerials and a conductive auxiliary agent for securement ofconductivity of the active material molded body 2 may be included in thestacked body 10. However, in this embodiment, during molding of theactive material molded body 2, the molding is performed without usingthe binder, the conductive auxiliary agent, and the like, and the activematerial molded body 2 is constituted by almost an inorganic material.Specifically, in this embodiment, a mass reduction rate when heating theelectrode composite body 4 at 400° C. for 30 minutes is set to 5% bymass or less. In addition, it is preferable that the mass reduction rateis 3% by mass or less, more preferably 1% by mass or less, and stillmore preferably a range in which the mass reduction is not observed, oran error range. Since the electrode composite body 4 has this massreduction rate, a material such as a solvent and absorbed water whichare evaporated under predetermined heating conditions, and an organicmaterial that is combusted or oxidized, and is vaporized underpredetermined heating conditions is included in the electrode compositebody 4 only by 5% by mass or less on the basis of the entirety of theconfiguration.

In addition, the mass reduction rate of the electrode composite body 4can be calculated as follows by using a thermogravimetry-differentialthermal analyzer (TG-DTA). First, the electrode composite body 4 isheated under predetermined heating conditions, the mass of the electrodecomposite body 4 after heating under the predetermined heatingconditions is measured, and the mass reduction rate is calculated from aratio between the mass before heating and the mass after heating.

In the stacked body 10 of this embodiment, a communication hole in whicha plurality of pores communicate with each other at the inside of theactive material molded body 2 in a network shape, and a solid portion ofthe active material molded body 2 also forms a network structure. Forexample, it is known that LiCoO₂ that is a positive electrode activematerial has anisotropy in electron conductivity of a crystal. Accordingto this, when forming an active material molded body by using LiCoO₂ asa formation material, in a configuration, in which pores extend in aspecific direction, similar to a case where pores are formed throughmachining, it is considered that electron conduction is less likely tooccur at the inside depending on a direction of a crystal which exhibitselectron conductivity. However, as is the case with the active materialmolded body 2, when the pores communicate with each other in a networkshape, and the solid portion of the active material molded body 2 hasthe network structure, it is possible to form a continuous surface,which is electrochemically active, without depending on the anisotropyin the electron conductivity or ion conductivity of a crystal. Accordingto this, it is possible to secure relatively satisfactory electronconductivity without depending on the kind of an active material that isused.

In addition, in the stacked body 10 of this embodiment, since theelectrode composite body 4 has the above-described configuration, theaddition amount of the binder or the conductive auxiliary agent which isincluded in the electrode composite body 4 is suppressed, and a capacitydensity per unit volume of the stacked body 10 is further improved incomparison to a case of using the binder or the conductive auxiliaryagent.

In addition, in the stacked body 10 (electrode composite body 4) of thisembodiment, the first solid electrolyte layer 3 also comes into contactwith a surface of the porous active material molded body 2 on an innerside of the pores. According to this, a contact area between the activematerial molded body 2 and the first solid electrolyte layer 3 furtherincreases in comparison to a case where the active material molded body2 is not a porous body, or a case where the first solid electrolytelayer 3 is not formed inside the pores, and thus it is possible toreduce interfacial impedance. Accordingly, satisfactory charge migrationis possible at an interface between the active material molded body 2and the first solid electrolyte layer 3.

Accordingly, in the lithium secondary battery 100 including the stackedbody 10, capacity per unit volume is further improved and higher outputis attained in comparison to other lithium secondary batteries which donot include the stacked body 10.

In addition, in the stacked body 10 of this embodiment, with regard tothe inside of the pores of the porous active material molded body 2, atleast a part of the voids, which are not buried in the first solidelectrolyte layer 3, is buried with the second solid electrolyte layer5. According to this, it is possible to enhance charge migration betweenthe active material molded body 2 and the first solid electrolyte layer3 by the second solid electrolyte layer 5, and it is also possible toenhance charge migration in the first solid electrolyte layer 3. As aresult, it is possible to attain additional high capacity and highoutput of the lithium secondary battery 100.

Particularly, the second inorganic solid electrolyte, which is includedin the second solid electrolyte layer 5, is less likely to be affectedby moisture, and has excellent charge mobility derived from acrystalline structure. According to this, in the electrode compositebody 4, high charge mobility is retained over a long period of time, andthus it is possible to secure long-term reliability of the lithiumsecondary battery 100.

In addition, in the electrode composite body 4 including the activematerial molded body 2, the first solid electrolyte layer 3, and thesecond solid electrolyte layer 5 as described above, the active materialmolded body 2 and the first solid electrolyte layer 3 are exposed fromthe one surface 4 a, and one or both of the first solid electrolytelayer 3 and the second solid electrolyte layer 5 are exposed from theother surface 4 b. In addition, in this state, the current collector 1is joined to the one surface 4 a, and the electrode 20 is joined to theother surface 4 b. According to this configuration, in the lithiumsecondary battery 100, it is possible to prevent the electrode 20 andthe current collector 1 from being connected through the active materialmolded body 2, that is, it is possible to prevent short-circuit.Accordingly, the first solid electrolyte layer 3 and the second solidelectrolyte layer 5 also function as a short-circuit prevention layerthat prevents short-circuit from occurring in the lithium secondarybattery 100.

The electrode 20 is provided on the other surface 4 b of the electrodecomposite body 4, which is opposite to the current collector 1, to comeinto contact with the first solid electrolyte layer 3 or the secondsolid electrolyte layer 5 without coming into contact with the activematerial molded body 2.

The electrode 20 functions as a negative electrode in a case where theactive material molded body 2 is constituted by a positive electrodeactive material, and functions as a positive electrode in a case wherethe active material molded body 2 is constituted by a negative electrodeactive material.

As a formation material (constituent material) of the electrode 20, in acase where the electrode 20 is a negative electrode, for example,lithium (Li) can be exemplified, and in a case where the electrode 20 isa positive electrode, for example, aluminum (Al) can be exemplified.

Although not particularly limited, for example, the thickness of theelectrode 20 is preferably 1 μm to 100 μm, and more preferably 20 μm to50 μm.

Next, description will be given of a method of manufacturing the lithiumsecondary battery 100 of the first embodiment (method of manufacturingthe electrode composite body according to the invention) which isillustrated in FIG. 1.

FIG. 2A to FIG. 8B are views illustrating the method of manufacturingthe lithium secondary battery illustrated in FIG. 1.

[1] First, description will be given of two methods of manufacturing theactive material molded body 2.

[1-1] FIGS. 2A and 2B are views illustrating a first method ofmanufacturing the active material molded body 2.

In the first method, the plurality of active material particles 21having a particle shape are heated to three-dimensionally connect theplurality of active material particles 21 to each other, therebyobtaining the active material molded body 2 that is constituted by aporous body.

For example, as illustrated in FIGS. 2A and 2B, the active materialmolded body 2 is obtained as follows. A mixture of the plurality ofactive material particles 21 is compressed and molded by using a mold Fhaving a space corresponding to a shape of the active material moldedbody 2 to be formed (refer to FIG. 2A), and the compression-molded bodythat is obtained is subjected to a heat treatment (refer to FIG. 2B).

It is preferable that the heating treatment is performed at a treatmenttemperature that is equal to or higher than 850° C. and is lower thanthe melting point of the lithium composite oxide that is used. Accordingto this, it is possible to reliably obtain a molded body in which theactive material particles 21 are sintered and integrated with eachother. When performing the heat treatment in the temperature range, evenwhen a conductive auxiliary agent is not added, resistivity of theactive material molded body 2, which is obtained, can be preferably setto 700 Ω/m or less. According to this, the lithium secondary battery100, which is obtained, can have a sufficient output.

At this time, when the treatment temperature is lower than 850° C.,sintering does not progress sufficiently and electron conductivityitself inside a crystal of the active material deteriorates depending onthe kind of lithium composite oxide that is used, and thus there is aconcern that a desired output may not be obtained in the lithiumsecondary battery 100 that is obtained.

In addition, the treatment temperature is higher than the melting pointof the lithium composite oxide, lithium ions excessively vaporize fromthe inside of a crystal of the lithium composite oxide, and the electronconductivity of the lithium composite oxide deteriorates, and thus thereis a concern that the capacity of the electrode composite body 4, whichis obtained, may decrease.

Accordingly, it is preferable that the treatment temperature is equal toor higher than 850° C. and lower than the melting point of the lithiumcomposite oxide to obtain an appropriate output and appropriatecapacity, more preferably 875° C. to 1000° C., and still more preferably900° C. to 920° C.

In addition, it is preferable that the heat treatment of this process isperformed for 5 minutes to 36 hours, and more preferably 4 hours to 14hours.

When the above-described heat treatment is performed, growth of a grainboundary inside the active material particles 21, or sintering betweenthe active material particles 21 progresses, and thus the activematerial molded body 2 that is obtained is likely to maintain a shape,and thus it is possible to reduce the amount of a binder that is addedto the active material molded body 2. In addition, bonds are formedbetween the active material particles 21 through the sintering, and thusit is possible to form a migration route of electrons between the activematerial particles 21. As a result, it is also possible to suppress theamount of the conductive auxiliary agent that is added.

In addition, as the formation material of the active material particles21, LiCoO₂ can be appropriately used. According to this, theabove-described effect can be more significantly exhibited. That is, itis possible to more reliably obtain the active material molded body 2 inwhich the active material particles 21 are sintered and integrated witheach other.

In addition, in the active material molded body 2 that is obtained, aplurality of the pores of the active material molded body 2 areconfigured as a communication hole in which the plurality of porescommunicate with each other in a network shape on an inner side of theactive material molded body 2.

In addition, an organic polymer compound such as polyvinylidene fluoride(PVDF) and polyvinyl alcohol (PVA) may be added to the formationmaterial, which is used to form the active material particles 21, as abinder. The binder is combusted or oxidized in the heat treatment of theprocess, and thus the amount of the binder is reduced.

In addition, a particle-shaped pore forming material, in which a polymeror a carbon powder is used as a formation material, is preferably addedto the above-described formation material, which is used, as a mold ofthe pores during compacting molding. When the pore forming material ismixed in, it is easy to control the porosity of the active materialmolded body 2. The pore forming material is decomposed and removedthrough combustion or oxidation during the heat treatment, and theamount of the pore forming material is reduced in the active materialmolded body 2 that is obtained.

An average particle size of the pore forming material is preferably 0.5μm to 10 μm.

In addition, it is preferable that the pore forming material includesparticles (first particles) in which a material having deliquescency isused as a formation material. When the first particles deliquesce,water, which occurs at the periphery of the first particles, functionsas a binder for joining of the particle-shaped lithium composite oxide,and thus it is possible to maintain a shape from compression molding ofthe lithium composite oxide having a particle shape to the heattreatment. According to this, it is possible to obtain the activematerial molded body without addition of another binder or whilereducing the amount of the binder that is added, and it is possible toeasily realize the electrode composite body with high capacity.

Examples of the first particles include particles in which polyacrylicacid is used as a formation material.

In addition, it is preferable that the pore forming material furtherincludes particles (second particles) in which a material having nodeliquescence is used as a formation material. The pore forming materialincluding the second particles is easy to handle. In addition, when thepore forming material having deliquescence, the porosity of the activematerial molded body may deviate from a desired setting value dependingon the amount of moisture at the periphery of the pore forming material,but when the second particles, which do not deliquesce, aresimultaneously included as the pore forming material, it is possible tosuppress the deviation in the porosity.

According to the above-described first method, it is possible to obtainthe active material molded body 2.

[1-2] Next, description will be given of a second method ofmanufacturing the active material molded body 2. The active materialmolded body 2 may be obtained by using a method in which slurry thatcontains the active material particles 21 is heated in addition to themethod in which the active material particles 21 are compressed andmolded, and the resultant molded body is heated as described above.

FIGS. 3A and 3B are views illustrating the second method ofmanufacturing the active material molded body 2.

The second method includes a preparation process of preparing slurrythat contains the active material particles 21, and a drying process ofheating the slurry to obtain the active material molded body 2.Hereinafter, the processes will be described.

First, a binder is dissolved in a solvent, and the active materialparticles 21 are dispersed in the resultant mixture to prepare slurry26. In addition, a dispersing agent such as oleylamine may be includedin the slurry 26.

Then, a mold F2, which includes a lower portion F21 having a concaveportion F25, and a lid portion F22, is prepared, and the slurry 26 issupplied dropwise to the concave portion F25 of the lower portion F21,and then the lower portion F21 is covered with the lid portion F22(refer to FIGS. 3A and 3B).

In addition, the total amount of the active material particles 21contained in the slurry 26 is preferably 10% by mass to 60% by mass, andmore preferably 30% by mass to 50% by mass. According to this, asdescribed later, the active material molded body 2 having a preferableporosity is obtained.

In addition, although not particularly limited, examples of the binderinclude a cellulose-based binder, an acryl-based binder, a polyvinylalcohol-based binder, a polyvinyl butyral-based binder, and the like inaddition to polycarbonate, and these may be used alone or in acombination of two or more kinds thereof.

In addition, although not particularly limited, as the solvent, forexample, an aprotic solvent is preferable. According to this, it ispossible to reduce deterioration of the active material particles 21 dueto contact with the solvent.

Specific examples of the aprotic solvent include butanol, ethanol,propanol, methyl isobutyl ketone, toluene, xylene, and the like, and asingle solvent or a mixed solvent thereof can be used as the solvent.

Next, the slurry 26, which contains the active material particles 21, isheated to dry the slurry 26 and to sinter the active material particles21 which are contained in the slurry 26, thereby obtaining the activematerial molded body 2.

In addition, a heating temperature during heating of the slurry 26 isset to the same conditions during the heat treatment of thecompression-molded body as described above.

In addition, it is preferable that heating of the slurry 26 is performedin a multi-stage in which a temperature condition rises step by step.Specifically, it is preferable that after drying to room temperature, atemperature is raised from room temperature to 300° C. for 2 hours, thetemperature is raised to 350° C. for 0.5 hours, the temperature israised to 1000° C. for 2 hours, and then the concave portion F25 iscovered with the lid portion F22, and baking is performed at 1000° C.for 8 hours. When the temperature is raised under the conditions, it ispossible to reliably bake out the binder that is included in thesolvent.

According to the second method, it is also possible to obtain the activematerial molded body 2.

[2] Next, description will be given of two methods of manufacturing theelectrode composite body 4 by impregnating the first solid electrolytelayer 3 and the second solid electrolyte layer 5 into the activematerial molded body 2.

[2-1] FIGS. 4A and 4B, and FIGS. 5A and 5B are views of illustrating afirst method of manufacturing the electrode composite body 4.

In the first method, first, as illustrated in FIGS. 4A and 4B, a liquidsubstance 3X, which includes a precursor of the first inorganic solidelectrolyte, is applied to the surface, which includes a surface of theactive material molded body 2 on an inner side of the pores, of theactive material molded body 2 so as to impregnate the active materialmolded body 2 with the liquid substance 3X (refer to FIG. 4A). Then, theactive material molded body 2 is baked to convert the precursor to thefirst inorganic solid electrolyte, thereby forming the first solidelectrolyte layer 3 (refer to FIG. 4B).

The liquid substance 3X may include a solvent, in which the precursor issoluble, in addition to the precursor. In a case where the liquidsubstance 3X includes the solvent, for example, after the application ofthe liquid substance 3X by a dispenser D and the like, the solvent maybe appropriately removed before baking. It is possible to employ amethod selected from typically known methods such as heating,decompression, and blowing, or a method in which two or more kinds ofthe methods are combined for removal of the solvent.

As described above, since the first solid electrolyte layer 3 is formedthrough application of the liquid substance 3X having flowability, thefirst solid electrolyte layer 3 is also formed on a surface of the fineactive material molded body 2 on an inner side of the pores. Accordingto this, it is easy to increase a contact area between the activematerial molded body 2 and the first solid electrolyte layer 3, and acurrent density at the interface between the active material molded body2 and the first solid electrolyte layer 3 is reduced. As a result, it ispossible to attain high output of the lithium secondary battery 100.

In addition, the first inorganic solid electrolyte is generated bybaking (heating) the precursor of the first inorganic solid electrolyteas described later, and during the baking, at least a part of the firstinorganic solid electrolyte that is generated forms the granular bodies31 each of which is composed of a secondary particle that is formedthrough granulation of primary particles. Accordingly, at least a partof the first solid electrolyte layer 3 is also formed inside the pores(voids) of the fine active material molded body 2, and is provided as anaggregate of the granular bodies 31. According to this, as is the casewith the active material molded body 2, at least a part of the firstsolid electrolyte layer 3 is also formed as a porous body. Accordingly,the first solid electrolyte layer 3 is formed to fill the voids of theactive material molded body 2, but a part of the voids also remains evenafter the filling.

Examples of the precursor of the first inorganic solid electrolyteinclude the following (A), (B), and (C).

(A) A composition that includes metal atoms of the first inorganic solidelectrolyte in a ratio according to a compositional formula of the firstinorganic solid electrolyte, and has a salt that becomes the firstinorganic solid electrolyte through oxidation.

(B) A composition having a metal alkoxide that includes metal atoms ofthe first inorganic solid electrolyte in a ratio according to acompositional formula of the first inorganic solid electrolyte.

(C) A dispersed solution in which fine particles of the first inorganicsolid electrolyte, or fine particle sol including metal atoms of thefirst inorganic solid electrolyte in a ratio according to acompositional formula of the first inorganic solid electrolyte isdispersed in a solvent or (A) or (B).

In addition, the salt that is included in (A) includes a metal complex.In addition, (B) is a precursor in a case of forming the first inorganicsolid electrolyte by using a so-called sol-gel method. In (A) and (B),the granular bodies 31 are generated through a reaction of theprecursor. In addition, in (C), a dispersion medium is removed togenerate the granular bodies 31.

The precursor of the first inorganic solid electrolyte is baked under anatmospheric atmosphere at a temperature lower than the temperatureduring the heat treatment to obtain the active material molded body 2.Specifically, a baking temperature is preferably set to a temperaturerange of 300° C. to 800° C. According to this, the first inorganic solidelectrolyte is generated from the precursor through the baking, and thusthe first solid electrolyte layer 3 is formed.

When the baking is performed in the above-described temperature range,at an interface between the active material molded body 2 and the firstsolid electrolyte layer 3, it is possible to prevent a solid phasereaction from occurring due to mutual diffusion of elements whichrespectively constitute the active material molded body 2 and the firstsolid electrolyte layer 3, and it is possible to suppress generation ofa by-product that is electrochemically inactive. In addition,crystallinity of the first inorganic solid electrolyte is improved, andthus it is possible to improve ion conductivity of the first solidelectrolyte layer 3. In addition, sintering of a portion occurs at theinterface between the active material molded body 2 and the first solidelectrolyte layer 3, and thus charge migration at the interface becomeseasy. According to this, the capacity or the output of the lithiumbattery that uses the electrode composite body 4 is improved.

In addition, the baking may be performed through one heat treatment, ormay be performed by dividing the heat treatment into a first heattreatment in which the precursor is deposited on the surface of theporous body, and a second heat treatment in which heating is performedunder a temperature condition that is equal to or higher than atreatment temperature in the first heat treatment and equal to or lowerthan 800° C. When the baking is performed through the heat treatmentperformed step by step, it is possible to easily form the first solidelectrolyte layer 3 at a desired position.

Next, as illustrated in FIG. 5A, a powder 5X (solid material) of thesecond inorganic solid electrolyte is supplied to the surface of theactive material molded body 2 and the first solid electrolyte layer 3.

The powder 5X may be supplied in a state of having flowability as apowder, or may be supplied in a state of being solidified in a sheetshape, a block shape, or the like (for example, a cube sular-likestate).

In addition, a position to which the powder 5X is supplied is notparticularly limited as long as the powder 5X comes into contact withthe active material molded body 2 and the first solid electrolyte layer3 at the position, and the powder 5X may be supplied to an uppersurface, a lateral surface, or the entirety of surfaces.

In addition, although not particularly limited, it is preferable that anaverage particle size of the powder 5X is 0.5 μm to 500 μm, and morepreferably 1 μm to 100 μm. When the average particle size of the powder5X is set in the above-described range, when heating the powder 5X, itis possible to uniformly melt the entirety of the powder 5X in a shortperiod of time. According to this, it is possible to impregnate theresultant molten material to the every corner inside the pores of theactive material molded body 2.

In addition, for example, the average particle size of the powder 5X isobtained as a particle size at 50% from a small diameter side on thebasis of the mass in a particle size distribution obtained by a laserdiffraction method.

Next, the powder 5X is heated. According to this, the powder 5X ismelted, and a molten material of the second inorganic solid electrolyteis generated. The molten material of the second inorganic solidelectrolyte is impregnated into the pores of the active material moldedbody 2, that is, the voids which are not buried with the first solidelectrolyte layer 3. That is, the molten material of the secondinorganic solid electrolyte is in a liquid state, and has excellentflowability that is specific to a liquid. According to this, it is alsopossible to efficiently impregnate the molten material into narrowvoids. In addition, as described later, the molten material, which isimpregnated into the voids, is solidified, and thus the second solidelectrolyte layer 5, which fills the pores of the active material moldedbody 2 at a relatively high filling factor, is obtained. As a result, itis possible to attain high capacity and high output of the lithiumsecondary battery 100.

In addition, in the method, since the molten material of the powder 5Xis impregnated, it is possible to minimize a decrease in volume duringsolidification, for example, in comparison to a method of impregnating adispersed solution obtained by dispersing the powder 5X in a dispersingmedium and the like. In other words, a material such as the dispersingmedium to be removed is not included, and thus a decrease in volumeduring solidification is suppressed. According to this, the second solidelectrolyte layer 5 can more closely fill the pores of the activematerial molded body 2, and can contribute to realization of a morestable charge and discharge cycle.

A heating temperature for the powder 5X may be equal to or higher thanthe melting point of the second inorganic solid electrolyte, and ispreferably lower than 800° C. According to this, it is possible toprevent mutual diffusion from occurring between the first solidelectrolyte layer 3 and the second solid electrolyte layer 5. As aresult, it is possible to suppress deterioration of characteristics ofthe first solid electrolyte layer 3 and the second solid electrolytelayer 5. In addition, as an example, the heating temperature for thepowder 5X may be 650° C. to 750° C.

In addition, a heating time for the powder 5X is not particularlylimited as long as the entirety of powder 5X can be melted, and as anexample, the heating time is 1 minute to 2 hours, and preferably 3minutes to 1 hour.

Next, the molten material of the powder 5X is solidified. According tothis, the molten material becomes a solid and is crystallized at theinside of the pores of the active material molded body 2. As a result,the second solid electrolyte layer 5, which is crystalline, is formed(refer to FIG. 5B).

The solidification of the molten material may be performed by a methodin which the molten material is left as is (natural heat radiation), ora method of compulsorily radiating heat of the molten material. However,when cooling is performed quickly, there is a concern that a greatthermal shock may be applied depending on a cooling rate, and thus it ispreferable that the molten material is solidified through slow cooling.

In addition, a grain size of crystals included in the second solidelectrolyte layer 5 that is formed can be made to be relatively smallerby setting a heat radiation rate to be fast, and the grain size ofcrystals, which are formed, can be made to be relatively larger bysetting the heat radiation rate to be slow. Accordingly, it is possibleto adjust the grain size of the crystals which are included in thesecond solid electrolyte layer 5 by appropriately changing the heatradiation rate.

As described above, the electrode composite body 4 including the activematerial molded body 2, the first solid electrolyte layer 3, and thesecond solid electrolyte layer 5 is obtained.

[2-2] FIGS. 6A and 6B are views illustrating a second method ofmanufacturing the electrode composite body 4. In addition, hereinafter,description will be mainly given of a difference from the first method,and description of the same configuration will not be repeated.

In the second method, first, as illustrated in FIG. 6A, a powder 3Y(solid material) of the first inorganic solid electrolyte, and a powder5X (solid material) of the second inorganic solid electrolyte aresupplied to the surface of the active material molded body 2.

The powder 3Y and the powder 5X may be respectively supplied in a stateof having flowability as a powder, or may be respectively supplied in astate of being solidified in a sheet shape, a block shape, or the like.

In addition, a position to which the powder 3Y and the powder 5X aresupplied is not particularly limited as long as the powder 3Y and thepowder 5X come into contact with the active material molded body 2 atthe position, and the powder 3Y and the powder 5X may be supplied to anupper surface, a lateral surface, or the entirety of surfaces.

Next, the powder 5X is heated. According to this, the powder 5X ismelted, and a molten material of the second inorganic solid electrolyteis generated. The molten material of the second inorganic solidelectrolyte is impregnated into the pores of the active material moldedbody 2. That is, the molten material of the second inorganic solidelectrolyte is in a liquid state, and has excellent flowability that isspecific to a liquid. According to this, it is also possible toefficiently impregnate the molten material into narrow pores. Inaddition, as described later, the molten material, which is impregnatedinto the pores, is solidified, and thus the second solid electrolytelayer 5, which fills the pores of the active material molded body 2 at arelatively high filling factor, is obtained.

On the other hand, in the second method, as the second inorganic solidelectrolyte, an electrolyte having the melting point lower than that ofthe first inorganic solid electrolyte is selected. Since the secondinorganic solid electrolyte is selected, when heating and melting thepowder 5X, it is possible to prevent the powder 3Y from being melted byappropriately setting a heating temperature.

Accordingly, a heating temperature for the powder 5X is set to be equalto or higher than the melting point of the second inorganic solidelectrolyte, and is lower than the melting point of the first inorganicsolid electrolyte.

In addition, as described above, the second inorganic solid electrolyteis an inorganic solid electrolyte that contains boron as a constituentelement. Although slightly different depending on the entirecomposition, when containing boron as a constituent element, the meltingpoint of the solid electrolyte can be lowered. Accordingly, in thisembodiment, since the boron-containing electrolyte is used as the secondinorganic solid electrolyte, it is easy to make the melting point of thesecond inorganic solid electrolyte to be lower than the melting point ofthe first inorganic solid electrolyte. In other words, since theboron-containing electrolyte is used, it is possible to realize thesecond inorganic solid electrolyte having the melting point lower thanthat of the first inorganic solid electrolyte without making a sacrificeof characteristics of the solid electrolyte such as lithium ionconductivity and insulating properties, and thus it is possible toenhance a filling factor with an electrolyte while maintaining chargemobility in the electrode composite body 4.

In addition, in this method, the molten material of the powder 5X isimpregnated, and thus it is possible to minimize a decrease in volumeduring solidification, for example, in comparison to a method ofimpregnating a dispersed solution obtained by dispersing the powder 5Xin a dispersing medium and the like. In other words, a material such asthe dispersing medium to be removed is not included, and thus a decreasein volume during solidification is suppressed. According to this, thesecond solid electrolyte layer 5 can more closely fill the pores of theactive material molded body 2, and can contribute to realization of amore stable charge and discharge cycle.

In addition, the powder 3Y and the powder 5X are supplied to the sameposition, and thus the powder 3Y is trapped by the powder 5X that ismelted. According to this, a liquid molten material, in which the powder3Y is dispersed, is obtained. The molten material, which includes thepowder 3Y as described above, is in a liquid state as a whole whilemaintaining characteristics as a powder by the powder 3Y.

Accordingly, when melting the powder 5X, a molten material of the powder5X can be allowed to enter the pores of the active material molded body2 while being accompanied with the powder 3Y. According to this, it ispossible to transfer the powder 3Y into the pores of the active materialmolded body 2 by using flowability of the molten material of the powder5X as a driving force.

Accordingly, finally, it is possible to fill the pores of the activematerial molded body 2 with the first solid electrolyte layer 3 and thesecond solid electrolyte layer 5 at a high filling factor. As a result,it is possible to attain high capacity and high output of the lithiumsecondary battery 100.

In addition, although not particularly limited, an average particle sizeof the powder 3Y is preferably 0.5 μm to 500 μm, and more preferably 1μm to 100 μm. When the average particle size of the powder 3Y is set inthe range, it is possible to efficiently allow the powder 3Y topenetrate into the pores of the active material molded body 2. Accordingto this, it is possible to impregnate the powder 3Y to the every cornerinside the active material molded body 2.

In addition, for example, the average particle size of the powder 3Y isobtained as a particle size at 50% from a small diameter side on thebasis of the mass in a particle size distribution obtained by a laserdiffraction method.

Next, the molten material of the powder 5X is solidified. According tothis, the molten material becomes a solid and is crystallized. As aresult, the second solid electrolyte layer 5, which is crystalline, isformed (refer to FIG. 6B).

The solidification of the molten material may be performed by a methodin which the molten material is left as is (natural heat radiation), ora method of compulsorily radiating heat of the molten material.

A grain size of crystals included in the second solid electrolyte layer5 that is formed can be made to be relatively smaller by setting a heatradiation rate to be fast, and the grain size of crystals, which areformed, can be made to be relatively larger by setting the heatradiation rate to be slow. Accordingly, it is possible to adjust thegrain size of the crystals which are included in the second solidelectrolyte layer 5 by appropriately changing the heat radiation rate.

In addition, at least a part of the powder 3Y aggregates to generate thegranular bodies 31. According to this, the first solid electrolyte layer3 is formed.

As described above, the electrode composite body 4 including the activematerial molded body 2, the first solid electrolyte layer 3, and thesecond solid electrolyte layer 5 is obtained.

[2-3] In addition, although not illustrated, description will be givenof a third method of manufacturing the electrode composite body 4.

In the third method, for example, LLZNb is generated in a LCBO flux. Inaddition, the active material molded body 2 is impregnated with theresultant solution that is obtained.

Then, the solution is dried, and thus the first solid electrolyte layer3 and the second solid electrolyte layer 5 are formed, thereby obtainingthe electrode composite body 4.

[3] Then, the electrode composite body 4 may be compressed to be moldedagain as necessary.

Examples of a method of compressing the electrode composite body 4include a method in which the electrode composite body 4 is accommodatedin a space provided to a mold F that is used in the above-describedprocess, and in this state, the volume of the space is shrunk asillustrated in FIG. 7A.

Here, as described above, the active material molded body 2 includesvoids, but the voids are filled with the first solid electrolyte layer 3and the second solid electrolyte layer 5. However, there is apossibility that voids, which are not filled, may partially exist. Inthese voids, for example, the granular bodies 31 come into contact witheach other in a point contact manner, and the active material particles21 and the granular bodies 31 also come into contact with each other ina point contact manner. There is a concern that the above-describedpoint contact may cause a decrease in lithium ion conductivity at apoint contact portion, and thus high output of the lithium secondarybattery 100 may deteriorate.

Accordingly, the electrode composite body 4 is compressed to be moldedagain, thereby shrinking voids which remain inside the electrodecomposite body 4. In addition, typically, the granular bodies 31 areharder than the active material particles 21, and thus when compressingthe electrode composite body 4, the active material particles 21 slideagainst each other, and thus the electrode composite body 4 is moldedagain. According to this, the voids are shrunk, and the granular bodies31 with a void interposed therebetween come into contact with eachother, or the active material particles and the granular bodies 31 witha void interposed therebetween come into contact with each other. Inaddition, a portion in which the contact occurs already contributes toan increase in a contact area. As a result, the lithium ion conductivitybetween the active material particles 21 and the granular bodies 31, andbetween the granular bodies 31 becomes excellent, and thus additionalhigh output of the lithium secondary battery 100 is attained.

A pressure for compressing the electrode composite body 4 is preferably10 N/mm² to 1000 N/mm², more preferably 50 N/mm² to 500 N/mm², and stillmore preferably 100 N/mm² to 400 N/mm². When the pressure is lower thanthe lower limit, there is a concern that shrinkage of the voids may bedifficult. In addition, when the pressure is higher than the upperlimit, there is a concern that the electrode composite body 4 may bebroken.

In addition, the time taken for compression of the electrode compositebody 4 is preferably 1 second to 600 seconds, more preferably 30 secondsto 600 seconds, and still more preferably 30 seconds to 180 seconds. Ina case where the time taken for the compression of the electrodecomposite body 4 is shorter than the lower limit, it is difficult touniformly compress the electrode composite body 4, and there is aconcern that it is difficult to enlarge a contact area between thegranular bodies 31 over the entirety of the electrode composite body 4.In addition, the time taken for the compression is longer than the upperlimit, time, which is necessary for this process, is unnecessarilylengthened, and thus there is a concern that a decrease in manufacturingefficiency may be caused.

In addition, it is preferable to heat the electrode composite body 4during compression of the electrode composite body 4. According to this,a connection force, which connects the active material particles 21which form the active material molded body 2, is reduced. Accordingly,it is possible to allow the active material particles 21 to reliablyslide against each other, and thus it is possible to reliably shrinkvoids which remain in the electrode composite body 4.

A temperature of heating the electrode composite body 4 is preferablylower than a temperature during the heat treatment for obtaining theactive material molded body 2 under the atmospheric atmosphere.Specifically, the temperature is more preferably in a range of 300° C.to 700° C. According to this, at an interface between the activematerial molded body 2 and the first solid electrolyte layer 3, aninterface between the first solid electrolyte layer 3 and the secondsolid electrolyte layer 5, and an interface between the active materialmolded body 2 and the second solid electrolyte layer 5, it is possibleto suppress generation of a by-product, which is electrochemicallyinactive, due to the occurrence of a solid phase reaction by mutualdiffusion of elements which respectively constitute the active materialmolded body 2, the first solid electrolyte layer 3, and the second solidelectrolyte layer 5.

In addition, in a case of performing the heat treatments in (B) and (C),it is preferable that the heat treatment time in each of the heattreatments is set to 5 minutes to 36 hours, and more preferably 4 hoursto 14 hours.

In addition, I) the heating of the electrode composite body 4 may beperformed simultaneously with the compression of the electrode compositebody 4, II) the heating may be performed prior to the compression of theelectrode composite body 4, or III) the heating may be performed afterthe compression of the electrode composite body 4. In addition, I), II),and III) may be performed in combination, and a combination of I) andII) is more preferable. According to this, it is possible to allow theactive material particles 21 to reliably slide against each otherwithout generating a crack and the like at a connection portion at whichthe active material particles 21 are connected to each other, and thusit is possible to shrink voids which remain in the electrode compositebody 4.

In addition, in a case of a combination of I) to III), when heatingtemperatures at I), II), and III) are set to I [° C.], II [° C.], andIII [° C.], respectively, it is preferable to satisfy a relationship ofAccording to this, it is possible to allow the active material particles21 to reliably slide against each other without generating a crack andthe like at a connection portion at which the active material particles21 are connected to each other, and thus it is possible to shrink voidswhich remain in the electrode composite body 4. In addition, it ispossible to reliably connect the active material particles 21 which areallowed to slide against each other. That is, an improvement in thestrength of the active material molded body 2 that is molded again isattained.

[4] Next, the one surface 4 a of the electrode composite body 4 isground and polished to expose the active material molded body 2, thefirst solid electrolyte layer 3, and the second solid electrolyte layer5 from the one surface 4 a (refer to FIG. 7B).

In this case, scratches (grinding and polishing scratches) which aretraces of the grinding and polishing remain on the one surface 4 a.

In addition, in the process, when forming the electrode composite body4, the active material molded body 2, the first solid electrolyte layer3, and the second solid electrolyte layer 5 are exposed from the onesurface 4 a. In this case, the grinding and polishing with respect tothe one surface 4 a of the electrode composite body 4 may be omitted,that is, this process may be omitted.

In addition, this process may be performed prior to the compression ofthe electrode composite body 4.

[5] Next, as illustrated in FIG. 8A, the current collector 1 is joinedto the one surface 4 a of the electrode composite body 4.

According to this, the stacked body 10 including the active materialmolded body 2, the first solid electrolyte layer 3, the second solidelectrolyte layer 5, and the current collector 1 is formed.

The joining of the current collector 1 may be performed by joining thecurrent collector 1, which is formed as a separate member, to the onesurface 4 a of the electrode composite body 4, or may be performed byforming a film of a formation material of the current collector 1 to theone surface 4 a of the electrode composite body 4 to form the currentcollector 1 on the one surface 4 a of the electrode composite body 4.

As a method of forming the current collector 1, various physical vapordeposition (PVD) methods and chemical vapor deposition (CVD) methods canbe used.

In this manner, the electrode composite body 4 and the stacked body 10are obtained. In addition, after the electrode composite body 4 isformed on an arbitrary member and is peeled off, the electrode compositebody 4 may be joined to the current collector 1 to manufacture thestacked body 10.

Next, description will be given of a method of manufacturing the lithiumsecondary battery 100 in which the stacked body 10 including theelectrode composite body 4 is used.

[6] Next, the lithium secondary battery 100 is formed by using thestacked body 10.

As described above, the stacked body 10 is a structure capable of beingused as one electrode of a battery, and thus it is possible to form thebattery by joining the other electrode structure to the electrodecomposite body 4 that is included in the stacked body 10. After theabove-described process, the lithium secondary battery 100 is formedthrough the following processes.

The other surface 4 b can be flat by grinding and polishing the othersurface 4 b of the electrode composite body 4, and thus it is possibleto enhance adhesiveness between the other surface 4 b and the electrode20.

Next, as illustrated in FIG. 8B, an electrode 20, which is the otherelectrode structure, is joined to the other surface 4 b of the electrodecomposite body 4.

In addition, the joining of the electrode 20 may be performed by joiningthe electrode 20, which is formed as a separate body, to the othersurface 4 b of the electrode composite body 4, or by forming a film of aformation material of the electrode 20 on the other surface 4 b of theelectrode composite body 4 to form the electrode 20 on the other surface4 b of the electrode composite body 4.

In addition, as a film forming method of the electrode 20, the samemethod as in the film forming method of the current collector 1 can beused.

The lithium secondary battery 100 is manufactured through theabove-described processes.

Second Embodiment

In this embodiment, description will be given of a lithium secondarybattery having a structure different from that of the first embodiment.In addition, in the following embodiments including this embodiment, thesame reference numerals will be given to the same constituent elementsas the constituent elements in the first embodiment, and descriptionthereof may not be repeated.

FIG. 9 is a longitudinal cross-sectional view of a lithium secondarybattery according to a second embodiment.

In a lithium secondary battery 100A, a third solid electrolyte layer 6is provided between the electrode composite body 4 and the electrode 20.

The third solid electrolyte layer 6, which is constituted by a thirdinorganic solid electrolyte different from the first inorganic solidelectrolyte or the second inorganic solid electrolyte, is providedbetween the electrode composite body 4 and the electrode 20.

When the third solid electrolyte layer 6 is provided, it is possible toprevent the current collector 1 and the electrode 20 from beingshort-circuited due to contact between the active material molded body 2and the electrode 20. Accordingly, even in a case where the activematerial molded body 2 is exposed from the other surface 4 b of theelectrode composite body 4, the third solid electrolyte layer 6functions as a short-circuit prevention layer (insulating layer) capableof preventing short-circuit between the current collector 1 and theelectrode 20. Accordingly, it is possible to stabilize the charge anddischarge cycle over a longer period of time.

As is the case with the first inorganic solid electrolyte or the secondinorganic solid electrolyte, the third inorganic solid electrolyte maybe a solid electrolyte capable of conducting lithium ions. In addition,a composition of the third inorganic solid electrolyte may be the sameas or different from the composition of the first inorganic solidelectrolyte or the composition of the second inorganic solidelectrolyte.

In addition, it is preferable that the third inorganic solid electrolyteis an inorganic solid electrolyte (boron-containing electrolyte) such asLi₂B₂O₄ and Li₃BO₃ which contain boron as a constituent element. Thethird inorganic solid electrolyte is less likely to be affected bymoisture, and thus it is possible to further enhance the long-termstability of the third solid electrolyte layer 6. As a result, thelithium secondary battery 100, which is obtained, has higherreliability.

In addition, the third inorganic solid electrolyte is less likely to bereduced with a potential of a negative electrode, and thus it ispossible to suppress reduction of the first solid electrolyte layer 3 orthe second solid electrolyte layer 5. According to this, deteriorationof the first solid electrolyte layer 3 or the second solid electrolytelayer 5 is suppressed, and thus it is possible to suppress a decrease incharge and discharge efficiency of the lithium secondary battery 100.

In addition, the third solid electrolyte layer 6 may be formed by anymethod, and examples of the method include a vapor phase film formationmethod such as a sputtering method and a vacuum deposition method, aliquid phase film formation method such as an application method and aspraying method, and the like. Among the methods, according to the vaporphase film formation method, it is possible to form the third solidelectrolyte layer 6 that is denser in comparison to an electrolyte layerformed by other methods. According to this, the above-described effect,which is exhibited by the third solid electrolyte layer 6, becomes moresignificant.

In addition, the third inorganic solid electrolyte may be crystalline oramorphous, but it is preferable that the third inorganic solidelectrolyte is amorphous. The third inorganic solid electrolyte, whichis amorphous, hardly includes a grain boundary, and thus structureuniformity is high. According to this, for example, even in a case whereexpansion and contraction of the third solid electrolyte layer 6repetitively occurs in accordance with charge and discharge of thelithium secondary battery 100 or a variation in temperature, or even ina case where the third solid electrolyte layer 6 receives a stress inaccordance with the expansion and contraction of the first solidelectrolyte layer 3 or the second solid electrolyte layer 5, the thirdsolid electrolyte layer 6 is less likely to mechanically deteriorate.Accordingly, it is possible to further enhance the long-term stabilityof the third solid electrolyte layer 6.

In addition, the third inorganic solid electrolyte, which is amorphous,is useful when considering that a decrease in lithium ion conductivityalong with a grain boundary is less likely to occur. That is, it ispossible to further enhance the reliability without making a sacrificeof the capacity or output of the lithium secondary battery 100.

In addition, according to the vapor phase film formation method, it iseasy to densely forma film of the third inorganic solid electrolyte withhigh degree of amorphousness, and thus the vapor phase film formationmethod is useful as a method of forming the third solid electrolytelayer 6.

In addition, in a case of using Li_(2.2)C_(0.8)B_(0.2)O₃ and Li₂B₂O₄ asthe second inorganic solid electrolyte and the third inorganic solidelectrolyte, respectively, the above-described effect becomes moresignificant.

Although not particularly limited, for example, an average thickness ofthe third solid electrolyte layer 6 is preferably 1 μm to 10 μm, andmore preferably 2 μm to 5 μm. When the thickness is set, the third solidelectrolyte layer 6, which has characteristics of both lithium ionconductivity and lithium reduction resistance, is obtained.

According to the lithium secondary battery 100A of the secondembodiment, the same effect as in the first embodiment is obtained.

Third Embodiment

In this embodiment, description will be given of a lithium secondarybattery having a structure different from that of the first embodimentand the second embodiment.

FIG. 10 is a longitudinal cross-sectional view of a lithium secondarybattery according to a third embodiment.

In a lithium secondary battery 100B, an electrode composite body 4Bhaving a configuration different from that of the electrode compositebody 4 is provided between the current collector 1 and the electrode 20to come into contact with the current collector 1 and the electrode 20.

The electrode composite body 4B includes an active material molded body2B including the active material particles 21 and noble metal particles22, the first solid electrolyte layer 3, and the second solidelectrolyte layer 5.

In other words, the electrode composite body 4B includes the activematerial molded body 2B, which includes the active material particles 21and the noble metal particles 22 which include a noble metal having amelting point of 1000° C. or higher and have a particle shape, insteadof the active material molded body 2 that is provided to the electrodecomposite body 4 in the first embodiment.

The noble metal particles 22 have a particle shape, and adhere to thesurface of the plurality of active material particles 21 which areconnected to each other, or are interposed between the active materialparticles 21.

According to this, delivery of electrons between the plurality of activematerial particles 21, and delivery of lithium ions between the activematerial particles 21, and the first solid electrolyte layer 3 and thesecond solid electrolyte layer 5 are performed through the noble metalparticles 22, and thus the delivery of the electrons and the delivery ofthe lithium ions can be smoothly performed. In addition, the delivery ofelectrons between the plurality of active material particles 21, and thedelivery of lithium ions between the active material particles 21, andthe first solid electrolyte layer 3 and the second solid electrolytelayer 5 are performed stably maintained over a long period of time.According to this, when the electrode composite body 4B having thisconfiguration is applied to the lithium secondary battery 100B, thelithium secondary battery 100B can stably maintain high output and highcapacity over a long period of time. It is preferable that the noblemetal particles 22 contain a noble metal having a melting point of 1000°C. or higher as a formation material (constituent material).

Although not particularly limited, examples of the noble metal having amelting point of 1000° C. or higher include gold (Au; melting point:1061° C.), platinum (Pt; melting point: 1768° C.), palladium (Pd;melting point: 1554° C.), rhodium (Rh; melting point: 1964° C.), iridium(Ir; melting point: 2466° C.), and ruthenium (Ru; melting point: 2334°C.), and osmium (Os; melting point: 3033° C.). These metals may be usedalone or an alloy of these metals may be used. Among these, at least onekind of platinum and palladium is preferable. Among noble metals, theabove-described noble metals can be easily treated at a relatively lowprice, and are excellent in conductivity of lithium ions and electrons.According to this, when the noble metals are used as a constituentmaterial of the noble metal particles 22, the delivery of electronsbetween the plurality of active material particles 21, and the deliveryof lithium ions between the active material particles 21, and the firstsolid electrolyte layer 3 and the second solid electrolyte layer 5 canbe smoothly performed, and can be stably maintained over a long periodof time.

In addition, it is preferable that an average particle size of the noblemetal particles 22 is 0.1 μm to 10 μm, and more preferably 0.1 μm to 5μm. In addition, the average particle size of the noble metal particles22 can be measured by using the same method as in the measurement of theaverage particle size of the active material particles 21.

In addition, it is preferable that the content rate of the noble metalparticles 22 in the active material molded body 2B is 0.1% by mass to10% by mass, and more preferably 1% by mass to 10% by mass.

When the average particle size and the content rate of the noble metalparticles 22 are set in the above-described ranges, it is possible toallow the noble metal particles 22 to adhere to the surface of theactive material particles 21 in a more reliable manner, or it ispossible to allow the noble metal particles 22 to be interposed betweenthe active material particles 21. As a result, the delivery of electronsbetween the plurality of active material particles 21, and the deliveryof lithium ions between the active material particles 21, and the firstsolid electrolyte layer 3 and the second solid electrolyte layer 5 canbe smoothly performed, and can be stably maintained over a long periodof time.

For example, the active material molded body 2B can be manufactured byadding the noble metal particles 22 in combination with the activematerial particles 21 in the above-described method of manufacturing thelithium secondary battery.

According to the lithium secondary battery 100B of the third embodiment,it is possible to obtain the same effect as in the first embodiment.

Hereinbefore, description has been given on the basis of the embodimentsin which the electrode composite body, the method of manufacturing theelectrode composite body, and the lithium battery according to theinvention are described, but the invention is not limited thereto.

For example, an arbitrary configuration may be added to the electrodecomposite body according to the invention and the lithium batteryaccording to the invention.

In addition, one or more arbitrary processes may be added to the methodof manufacturing the electrode composite body according to theinvention.

In addition, the lithium battery according to the invention may have aconfiguration in which two or more configurations of the lithiumbatteries of the respective embodiments are combined in an arbitrarymanner.

In addition, application according to the invention can be made invarious manners in a range not departing from the gist of the invention.

EXAMPLES

Next, description will be given of specific examples of the invention.

1. Manufacturing of Lithium Secondary Battery Example 1

<1> First, 100 parts by mass of powder-shaped LiCoO₂ (manufactured bySigma-Aldrich Co. LLC.) (hereinafter, many be referred to as “LCO”), and3 parts by mass of polyacrylic acid (PAA) (manufactured by Sigma-AldrichCo. LLC.) as a powder-shaped pore forming material were mixed with eachother while being crushed by using a mortar.

<2> Next, 80 mg of the resultant mixed powder was put into a dice havinga diameter of 11 mmφ and was compressed to mold a disc-shaped pallet.The molded pallet was sintered by performing a heat treatment in analumina crucible in which the LCO powder was placed on the bottom at1000° C. for 8 hours. During the heat treatment, a temperature raisingrate was set to 3° C./minute, and a temperature lowering rate was set to3° C./minute up to 500° C. to prepare a porous active material moldedbody. The thickness of the active material molded body that was obtainedwas approximately 300

<3> Next, a propionic acid solution of lithium acetate, a propionic acidsolution of lanthanum acetate 1.5 hydrates, zirconium butoxide, and2-butoxy ethanol solution of niobium penta ethoxide were stirred whilebeing heated at 90° C. for 30 minutes. Then, the resultant mixture wasslowly cooled down to room temperature to obtain a precursor solution ofLi_(6.8)La₃Zr_(1.8)Nb_(0.2)O₁₂ (hereinafter, referred to as LLZNb). Inaddition, during preparation of the precursor solution, raw materialswere weighed so that atoms of respective elements were contained in acompositional ratio in accordance with a compositional formula of LLZNb.

<4> Next, the precursor solution was impregnated to the active materialmolded body that was obtained in the process <2>, and drying wasperformed at 60° C. Then, heating was performed at 200° C. to depositthe precursor of LLZNb onto the active material molded body. Theoperations from the impregnation of the precursor solution to the activematerial molded body to heating at 200° C. were repeated before the massof the precursor that was deposited onto the active material molded bodyreached 15 mg that was a setting amount.

The precursor in the setting amount was deposited onto the activematerial molded body, and the entirety thereof was heated at 700° C. andwas baked, thereby obtaining a composite body in which the first solidelectrolyte layer was formed on the surface of the disc-shaped activematerial molded body.

<5> Next, 20 mg of Li_(2.2)C_(0.8)B_(0.2)O₃ (hereinafter, referred to as“LOBO”) powder, which was the second inorganic solid electrolyteprepared by mixing a Li₂CO₃ powder and a Li₃BO₃ powder in a ratio of10:2, and by sintering the resultant mixture, was loaded on the surfaceof the composite body that was obtained.

<6> Next, the composite body, on which the powder was loaded, was heatedat 700° C. for 10 minutes. According to this, the powder was melted toimpregnate the resultant molten material into the composite body.

<7> Next, the molten material was solidified through natural heatradiation. According to this, the molten material was crystallized toform the second solid electrolyte layer, thereby obtaining the electrodecomposite body.

<8> Next, mechanical polishing was performed with respect to bothopposite surfaces of the electrode composite body that was obtained.

In addition, polishing on a positive electrode side was performed untilthe active material molded body was exposed from a polished surface inorder for the active material molded body and an electrode to come intoelectrical contact with each other. In addition, on the assumption of asecond battery that includes an electrode composite body, polishing wasalso performed on a negative electrode side in consideration ofpackaging into a battery case.

<9> Next, an aluminum sheet as a current collector was joined to apositive electrode side. On the other hand, a lithium-resistant layer,lithium metal foil, and copper foil were stacked on a negative electrodeside in this order, and these were compressed to form an electrode.According to this, a lithium secondary battery was obtained. Inaddition, the lithium-resistant layer was formed by a liquid compositioncomposed of polymethyl methacrylate (PMMA) (manufactured by SokenChemical & Engineering Co., Ltd.), LiCoO₂, ethylene carbonate(manufactured by Sigma-Aldrich Co. LLC.), and dimethyl carbonate(Sigma-Aldrich Co. LLC.), and by drying and solidifying the liquidcomposition.

A lithium secondary battery was obtained through the above describedprocesses.

Example 2

A lithium secondary battery was obtained in the same manner as inExample 1 except that a third solid electrolyte layer constituted byLi₃BO₃ (hereinafter, referred to as “LBO”), which is the third inorganicsolid electrolyte, was formed instead of the lithium-resistant layer.

In addition, the third solid electrolyte layer was prepared by asputtering method, and LBO was amorphous.

Example 3

A lithium secondary battery was obtained in the same manner as inExample 2 except that Li_(6.6)La₃Zr_(1.6)Nb_(0.4)O₁₂ was used instead ofLLZNb.

Example 4

A lithium secondary battery was obtained in the same manner as inExample 2 except that Li_(6.0)La₃Zr_(1.0)Nb_(1.0)O₁₂ was used instead ofLLZNb.

Example 5

A lithium secondary battery was obtained in the same manner as inExample 2 except that Li_(2.4)C_(0.6)B_(0.4)O₃ was used instead of LCBO.

Example 6

A lithium secondary battery was obtained in the same manner as inExample 2 except that Li_(2.8)C_(0.2)B_(0.8)O₃ was used instead of LCBO.

Example 7

A lithium secondary battery was obtained in the same manner as inExample 2 except that Li_(0.35)La_(0.55)TiO₃ (hereinafter, referred toas “LLT”) was used instead of LLZNb that is the first inorganic solidelectrolyte.

Example 8

<1> First, an active material molded body was prepared in the samemanner as in Example 1.

<2> Next, powder-shaped LLZNb and powder-shaped LCBO were mixed witheach other, and the resultant mixed powder was loaded on the surface ofthe active material molded body.

<3> Next, the active material molded body, on which the mixed powder wasloaded, was heated at 700° C. for 10 minutes. According to this, theLCBO powder in the mixed powder was melted, and the molten material wasimpregnated into the composite body.

<4> Next, the molten material was solidified through natural heatradiation. According to this, the molten material was crystallized toform the second solid electrolyte layer and the first solid electrolytelayer, thereby obtaining an electrode composite body.

<5> Next, polishing was performed in the same manner as in Example 1,and the current collector and the electrode were joined to the electrodecomposite body, thereby obtaining a lithium secondary battery.

Comparative Example 1

A lithium secondary battery was obtained in the same manner as inExample 1 except that formation of the second solid electrolyte layerwas omitted.

Comparative Example 2

A lithium secondary battery was obtained in the same manner as inExample 8 except that formation of the second solid electrolyte layerwas omitted.

Reference Example 1

A lithium secondary battery was obtained in the same manner as inExample 1 except that amorphous Li₂SiO₃ was used instead of LCBO that isthe second inorganic solid electrolyte.

Reference Example 2

A lithium secondary battery was obtained in the same manner as inExample 8 except that amorphous Li₂SiO₃ was used instead of LCBO that isthe second inorganic solid electrolyte.

2. Evaluation of Lithium Secondary Battery

Evaluation of charge and discharge characteristics was performed withrespect to the lithium secondary batteries of respective Examples,respective Comparative Examples and Reference Examples.

The charge and discharge characteristics were measured by using amulti-channel charge and discharge evaluation apparatus (HJ1001SD8,manufactured by Hokuto Denko Corp.). The measurement was performed underconditions of a current density of 0.1 mA/cm, a constantcurrent-constant voltage operation in which a charge upper limit voltagewas set to 4.2 V, and a constant current operation in which a dischargelower limit voltage was set to 3.0 V.

As a result, respective Examples exhibited more satisfactory charge anddischarge characteristics in comparison to respective ComparativeExamples and respective Reference Examples. Particularly, in Examples 1,2, and 8, the tendency was significant.

The reason for this is considered as follows. That is, the second solidelectrolyte layer, which includes the second inorganic solid electrolytethat contains boron as a constituent element and is crystalline, isformed, and thus filling factor of the pores in the active materialmolded body is improved, and thus an electrical interface increases. Asa result, improvement in the charge mobility is attained.

In addition, in respective Examples, it was confirmed that the capacityand output were greater than those in respective Comparative Examplesand Reference Examples.

What is claimed is:
 1. An electrode composite body, comprising: anactive material molded body including active material particles whichinclude a lithium composite oxide and have a particle shape, and acommunication hole that is provided between the active materialparticles; a first solid electrolyte layer that is provided on a surfaceof the active material molded body, and includes a first inorganic solidelectrolyte; and a second solid electrolyte layer that is provided onthe surface of the active material molded body, and includes a secondinorganic solid electrolyte of which a composition is different from acomposition of the first inorganic solid electrolyte, and which containsboron as a constituent element and is crystalline.
 2. The electrodecomposite body according to claim 1, wherein the lithium composite oxideis LiCoO₂.
 3. The electrode composite body according to claim 1, whereinthe first inorganic solid electrolyte is Li_(7-x)La₃(Zr_(2-x),M_(x))O₁₂, in the formula, M represents at least one kind ofelement selected from Nb, Sc, Ti, V, Y, Hf, Ta, Al, Si, Ga, Ge, Sn, andSb, and X represents a real number of 0 to
 2. 4. The electrode compositebody according to claim 1, wherein the second inorganic solidelectrolyte is Li_(2+X)B_(X)C_(1-X)O₃ (X represents a real number thatis greater than 0 and less than 1).
 5. A method of manufacturing anelectrode composite body, comprising: supplying a solution of a firstinorganic solid electrolyte to come into contact with an active materialmolded body including active material particles which include a lithiumcomposite oxide and have a particle shape, and a communication hole thatis provided between the active material particles so as to impregnatethe solution into the communication hole; heating the active materialmolded body that is impregnated with the solution; supplying a solidmaterial of a second inorganic solid electrolyte, of which a compositionis different from a composition of the first inorganic solid electrolyteand contains boron as a constituent element, to come into contact withthe active material molded body; melting the solid material of thesecond inorganic solid electrolyte, and impregnating the resultantmolten material of the second inorganic solid electrolyte into thecommunication hole; and solidifying the molten material to becrystallized.
 6. A method of manufacturing an electrode composite body,comprising: supplying a solid material of a first inorganic solidelectrolyte and a solid material of a second inorganic solidelectrolyte, of which a melting point is lower than a melting point ofthe first inorganic solid electrolyte and which contains boron as aconstituent element, to come into contact with an active material moldedbody including active material particles which include a lithiumcomposite oxide and have a particle shape, and a communication hole thatis provided between the active material particles; melting the solidmaterial of the second inorganic solid electrolyte, and impregnating theresultant molten material of the second inorganic solid electrolyte intothe communication hole in combination with the solid material of thefirst inorganic solid electrolyte; and solidifying the molten materialto be crystallized.
 7. A lithium battery, comprising: the electrodecomposite body according to claim 1; a current collector that isprovided on one surface of the electrode composite body to come intocontact with the active material molded body; and an electrode that isprovided on the other surface of the electrode composite body to comeinto contact with the first solid electrolyte layer or the second solidelectrolyte layer.
 8. A lithium battery, comprising: the electrodecomposite body according to claim 2; a current collector that isprovided on one surface of the electrode composite body to come intocontact with the active material molded body; and an electrode that isprovided on the other surface of the electrode composite body to comeinto contact with the first solid electrolyte layer or the second solidelectrolyte layer.
 9. A lithium battery, comprising: the electrodecomposite body according to claim 3; a current collector that isprovided on one surface of the electrode composite body to come intocontact with the active material molded body; and an electrode that isprovided on the other surface of the electrode composite body to comeinto contact with the first solid electrolyte layer or the second solidelectrolyte layer.
 10. A lithium battery, comprising: the electrodecomposite body according to claim 4; a current collector that isprovided on one surface of the electrode composite body to come intocontact with the active material molded body; and an electrode that isprovided on the other surface of the electrode composite body to comeinto contact with the first solid electrolyte layer or the second solidelectrolyte layer.
 11. The lithium battery according to claim 7, furthercomprising: a third solid electrolyte layer that is provided between theelectrode composite body and the electrode, and includes a thirdinorganic solid electrolyte that contains boron as a constituent elementand is amorphous.